Suffering from allergies and asthma is likely to become more frequent due to the increased level of carbon dioxide (CO2) predicted over the coming decades if greenhouse gas emissions are not curbed, researchers warn.

Earlier studies revealed that increased CO2 leads to more eye-watering and sneeze-causing pollen.

But writing in the journal Environmental Health Perspectives, lead author Julie Wolf of the University of Maryland said that elevated CO2 concentrations also cause increased production of fungal spores, to which many people are acutely sensitive.

The report says that spore production in some areas could increase threefold if the projected level of CO2 for the year 2040 is actually reached.